Wishbringer is a good time and, while specifically made for beginners, is pretty satisfying for those who’ve played a few, too. Just a nice piece of work.
I think I played the first Zork as maybe my … sixth or seventh Infocom title? Something like that. Didn’t find it too hard by then, but then again if a puzzle stumps me for more than a couple of hours I often just hint on past it (puzzles aren’t really why I play … but fortunately, the Zork series has a lot going on for those of us who don’t really play for the puzzles).
You are past ‘beginner’ already, and into the phase where, were I you, I would be open to any game except maybe ‘Expert’ level. (i.e. Avoid stuff like Jigsaw and Spellbreaker.) Infocom-wise, I would say Zork I or Planetfall or Enchanter would all be great next steps for you, depending on your preferences regarding genre. All three of those have sequels – in the case of the Zork and Enchanter series, the sequels get more difficult.
Both the Zork series and the Enchanter series take place in the same fantasy-style universe; however, the Zork series is quite anachronistic and irreverent (though not exactly a comedy) whereas the Enchanter series tends to take itself somewhat more seriously. Wishbringer takes place in the Zork/Enchanter universe, but it follows more in the Enchanter tradition than in the Zork tradition; and it’s better written than all of the above. The Planetfall series has much the same partly-unserious tone as the Zork series, only in space.
Planetfall, Enchanter, and Wishbringer are my favourites of all the games I’ve referenced here, in that they most involved me in their worlds. The geographies of those games are burned into my mind — they are real places to me. I can’t say the same about the other games – not even Zork.
And remember: don’t open the envelope until the game tells you to.
(You are playing the Infocom games with the documentation in hand, right? And the feelies, even if in PDF or JPG format? It’s pretty much a necessity - not only it’s copy-protection, it’s way, way cool)
My direct answer to the question in your subject line would be absolutely not. All of us who played it when it was new were pretty close to beginners. I say go for it, and have fun!
Of course, unlike the old days (when the only source of hints was finding a friend who had already gotten past whatever puzzle was hanging you up), today there are plenty of sources of hints available. That should relieve some of the frustration that you might feel on some of the more difficult parts, but I would urge you not to be too quick to use them. To me, one of the great thrills of IF is when you struggle for hours, days or weeks over a puzzle; then the inspiration finally strikes you, and you smack yourself on the side of the head as you realize just how obvious the solution should have been!